Groovy: Transforming a String into a Multimap - collections

Question

So I have a String which looks a little something like this:
text = "foo/bar;baz/qux"
My end goal is to split this String into a Multimap like this:
["level1" : ["foo", "baz"], "level2" : ["bar", "qux"]]
I also added Multimap-support to LinkedHashMap's metaClass:
LinkedHashMap.metaClass.multiPut << { key, value ->
delegate[key] = delegate[key] ?: []; delegate[key] += value
}
The String needs to be split at semi-colon and then again at forwardslash. Currently I'm populating my Multimap within a nested for-loop but obviously there's a Groovier way of doing this. Thus I was wondering what my options are?
I'm thinking something along the lines of:
def final myMap = text.split(';')
.collectEntries { it.split('/')
.eachWithIndex { entry, index -> ["level${index + 1}" : entry] }}

Answer 1

You can use withDefault on your returned Map to get rid of the ternary:
def text = "foo/bar;baz/qux;foo/bar/woo"
def result = text.split(';')*.split('/').inject([:].withDefault {[]}) { map, value ->
value.eachWithIndex { element, idx ->
map["level${idx+1}"] << element
}
map
}
assert result == [level1:['foo', 'baz', 'foo'], level2:['bar', 'qux', 'bar'], level3:['woo']]
If you don't want duplicates in your results, then you can use a Set in your withDefault (then convert back to a List afterwards):
def text = "foo/bar;baz/qux;foo/bar/woo"
def result = text.split(';')*.split('/').inject([:].withDefault {[] as Set}) { map, value ->
value.eachWithIndex { element, idx ->
map["level${idx+1}"] << element
}
map
}.collectEntries { key, value -> [key, value as List] }
assert result == [level1:['foo', 'baz'], level2:['bar', 'qux'], level3:['woo']]

Answer 2

My take on it, I wouldn't consider it very clever but I find it much easier to read:
def myMap = [:]
text.split(';').eachWithIndex{ entry, index ->
myMap << ["level${index + 1}": entry.split('/')]
}
If you are using Groovy 2.4.0 or above, you could use the withIndex() method which has been added to java.lang.Iterable:
def myMap = text.split(';').withIndex().collect{ entry, index ->
["level${index + 1}": entry.split('/')]
}